Power generated from an internal combustion engine of a vehicle may be used to operate various vehicle systems including, for example, HVAC system, electronic system, and computer system, when the engine is running. When the engine is off, a vehicle battery may provide power to operate vehicle systems and to start the vehicle. However, providing power to vehicle systems from the vehicle battery when the engine is off will drain power from the battery until the battery has insufficient power to operate the vehicle systems including the starter to start the engine. As a result, vehicle operators that need to use the vehicle systems while the vehicle is parked may allow the vehicle to idle (i.e. run the engine at some minimal rpm to produce power from the engine). Examples of vehicles that may be idled while parked include police vehicles, ambulances, fire trucks, buses, and recreational vehicles (RV's). As the cost of fuel has increased and concerns about fuel conservation and the emission of pollutants has grown, it has become desirous to reduce or eliminate engine idling.
Accordingly, there is a need for improved apparatus as well as related methods that power the systems of the vehicle while the vehicle's engine is off